FUNCTIONAL DEVELOPMENT OF RETICULO-ENDOTHELIAL SYSTEM IN TOAD, XENOPUS LAEVIS (DAUDIN)

The development and extent of the phagocytic system in larval and adult Xenopus was determined by injections of colloidal carbon by various routes, followed by dissection and/or histological examination. It was shown that in young tadpoles of stage 48 (aged 7.5 days at 23°C), the small population of pericardial and peritoneal macrophages alone was responsible for phagocytosing intraperitoneally injected carbon. In later stages this population of macrophages in greatly increased, and the tubule cells of the pronephros and mesonephros are capable of ingesting both carbon and mammalian erythrocytes drained from the body cavity. Attention was drawn to a possible relationship between this localization of foreign material in the open kidney, and the lymphoid accumulations found there in Xenopus and other lower vertebrates. Blood‐ and lymph‐borne particles were removed mainly by cells of the spleen and liver in both tadpoles and adults: no phagocytic organs which could be described as lymph nodes were found at any stage. The findings suggest that the reticulo‐endothelial system of Xenopus is more primitive than that of Rana or Bufo. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company